From an Oregon State University Media Release (h/t to Leif Svalgaard)
Long debate ended over cause, demise of ice ages – may also help predict future
)
The above image shows how much the Earth’s orbit can vary in shape.
This process in a slow one, taking roughly 100,000 to cycle.
(Credit: Texas A&M University note: illustration is not to scale)
CORVALLIS, Ore. – A team of researchers says it has largely put to rest a long debate on the underlying mechanism that has caused periodic ice ages on Earth for the past 2.5 million years – they are ultimately linked to slight shifts in solar radiation caused by predictable changes in Earth’s rotation and axis.
In a publication to be released Friday in the journal Science, researchers from Oregon State University and other institutions conclude that the known wobbles in Earth’s rotation caused global ice levels to reach their peak about 26,000 years ago, stabilize for 7,000 years and then begin melting 19,000 years ago, eventually bringing to an end the last ice age.
The melting was first caused by more solar radiation, not changes in carbon dioxide levels or ocean temperatures, as some scientists have suggested in recent years.
“Solar radiation was the trigger that started the ice melting, that’s now pretty certain,” said Peter Clark, a professor of geosciences at OSU. “There were also changes in atmospheric carbon dioxide levels and ocean circulation, but those happened later and amplified a process that had already begun.”
The findings are important, the scientists said, because they will give researchers a more precise understanding of how ice sheets melt in response to radiative forcing mechanisms. And even though the changes that occurred 19,000 years ago were due to increased solar radiation, that amount of heating can be translated into what is expected from current increases in greenhouse gas levels, and help scientists more accurately project how Earth’s existing ice sheets will react in the future.
“We now know with much more certainty how ancient ice sheets responded to solar radiation, and that will be very useful in better understanding what the future holds,” Clark said. “It’s good to get this pinned down.”
The researchers used an analysis of 6,000 dates and locations of ice sheets to define, with a high level of accuracy, when they started to melt. In doing this, they confirmed a theory that was first developed more than 50 years ago that pointed to small but definable changes in Earth’s rotation as the trigger for ice ages.
“We can calculate changes in the Earth’s axis and rotation that go back 50 million years,” Clark said. “These are caused primarily by the gravitational influences of the larger planets, such as Jupiter and Saturn, which pull and tug on the Earth in slightly different ways over periods of thousands of years.”
That, in turn, can change the Earth’s axis – the way it tilts towards the sun – about two degrees over long periods of time, which changes the way sunlight strikes the planet. And those small shifts in solar radiation were all it took to cause multiple ice ages during about the past 2.5 million years on Earth, which reach their extremes every 100,000 years or so.
Sometime around now, scientists say, the Earth should be changing from a long interglacial period that has lasted the past 10,000 years and shifting back towards conditions that will ultimately lead to another ice age – unless some other forces stop or slow it. But these are processes that literally move with glacial slowness, and due to greenhouse gas emissions the Earth has already warmed as much in about the past 200 years as it ordinarily might in several thousand years, Clark said.
“One of the biggest concerns right now is how the Greenland and Antarctic ice sheets will respond to global warming and contribute to sea level rise,” Clark said. “This study will help us better understand that process, and improve the validity of our models.”
The research was done in collaboration with scientists from the Geological Survey of Canada, University of Wisconsin, Stockholm University, Harvard University, the U.S. Geological Survey and University of Ulster. It was supported by the National Science Foundation and other agencies.
UPDATE: Science now has the paper online, which is behind a paywall. The abstract is open though and can be read below:
| Science 7 August 2009:
Vol. 325. no. 5941, pp. 710 – 714 DOI: 10.1126/science.1172873 |
Research Articles
The Last Glacial Maximum
Peter U. Clark,1,* Arthur S. Dyke,2 Jeremy D. Shakun,1 Anders E. Carlson,3 Jorie Clark,1 Barbara Wohlfarth,4 Jerry X. Mitrovica,5 Steven W. Hostetler,6 A. Marshall McCabe7
1 Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
2 Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada.
3 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
4 Department of Geology and Geochemistry, Stockholm University, SE-10691, Stockholm, Sweden.
5 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
6 U.S. Geological Survey, Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
7 School of Environmental Science, University of Ulster, Coleraine, County Londonderry, BT52 1SA, UK.
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Leif Svalgaard (23:31:10) :
Nasif Nahle (22:11:24) :
What’s heat in Svalgaardish?
If we really want to be technical. heat energy is that energy that potentially can be transferred to another body without applying any external forces, but not the transfer itself. There is still heat energy even if no transfer takes place.
What a conundrum. Heat is not a form of energy, but it is energy in transit. If that energy is not emitted and/or absorbed, but stored into a system, it’s not heat, but internal energy, i.e. potential and kinetic energy.
What do you think about Van Ness?
As one schooled in the old way, I have to agree with Nasif that definitions are meant to be precise, necessary and sufficient. Heat need not equate to thermal energy. You can make gunpowder, which when cold can produce thermal energy. In my first post or so on CA I noted that temperatures on earth were a poor proxy for “heat flow” (not “heat”) but temperatures were all we had for a while, which was a pity.
While Nasif and Leif are quite close to agreement, they are unfortunately far more precise than some other commentators. In the recent past I have seen bloggers rather confused by differences between static and dynamic processes and units. Probably including me.
While on line, might I please ask Leif a little more about orbits and their future prediction? I gave a poor example of satellites needing orbital correction, but omitted I was thinking more of the Voyager type satellites and thinking away from Earth’s atmospheric drag. There were other reasons why Voyager paths were altered, but some were because prediction did not match actual path.
There are quite a number of names given to recurrent events, some of which are too irregular in time to be properly named as cycles. These recurrent effects can be shown singly as a function of time, but I have not had the pleasure of seeing all the known perturbations combined and presented as one illustration. As the illustration is calculated further into the future, the uncertainty will increase and I am interested in the error bounds as well.
The other graph that I would rather like to see is the actual change in total Earth temperature (a horrible concept!) as a result of past and projected orbit perturbations. I have a problem because I can’t think of how to measure the centres of mass of the Earth and the Sun, and also how constant they are. If one is to use classical Newtonian maths, the COM is a good starting pont but I confess I do not know it it was overaken a long time ago by models depart from point sources to ones which inject the change of specific gravity of parts of the Sun and earth inceasingly more distant from the putative centre – and which might move in relation to that centre.
In this exercise I do not seek a dirty actual case that includes impacts by other bodies, but more a clean case based on formal smooth maths but including observations like tallbloke (19:49:22) : made on 8.8.2009.
Leif, I note your comment “The VSOP82 theory is thought to be good to one million years, and the improved VSOP87 to much longer.” But this leaves me wondering about climate shifts on Earth that might not be explained by hindcasting these models.
@ur momisugly Leif…
Here a link which talks about your confusion and explains why internal energy is not heat:
http://www.physicsforums.com/library.php?do=view_item&itemid=121
I’d say it’s impossible for past ice ages to recur. Y’know, them being in the past and all.
Sekerob (01:44:48) : Gosh, whats up with that isotope 12 and 13 marker that identifies that the bulk of the CO2 increase is fuel burning and not from natural sources?
Well, it’s seriously impaired by being based on a lot of hand waving:
http://chiefio.wordpress.com/2009/02/25/the-trouble-with-c12-c13-ratios/
Whats up with the fact that the oceans/plants are only able to take out half of what humans are pumping into the air.
Well, clearly that’s not the case:
First off, look at the “where carbon goes” graphic on the C12 – 13 link. Notice that total fossil fuels and cement is “5.5” while ocean is 92 and vegetation is 121.3? Do ya think that maybe 213 is bigger than 5.5?
(all numbers in Giga tons / year). Then read down to where it references a story about “fish gut rocks” sequestering hugh tons of carbonate that we don’t have a clue about.
Then take a look at:
http://chiefio.wordpress.com/2009/06/02/of-trees-volcanos-and-pond-scum/
Since a very simple “thought experiment” shows that plants can, and do, suck down all the CO2 we could put out,and then some, until they are metabolism limited due to CO2 shortage in the air. As more CO2 is added, they ramp up absorption until about 2000 ppm. The more we add, the faster they scrub (and grow, and feed us, and make timber, and…)
And per CO2 from volcanos: Once someone has managed to actually measure all the CO2 from mid-ocean ridges, I’ll start to consider that they might have a tiny bit of clue. Not before. Heck, we don’t even know for sure how many, what size, and how active the volcanos are under the ice cap of the Antarctic and under the Arctic ocean. Oh, and I presume your “annual average” does not include those times when we have a Supervolcano blow off or something like the massive basalt flows in India.
Oh, wait, supervolcanic eruptions make the world colder with all their CO2… Guess it’s not about the CO2 after all… must be the particulate matter or the sulphates or the winds or the…
The simple fact is that climate, ice ages, and volcanos all have cyclicality and non-cyclical variations that happen on the scale of 1000s to 10000s of years. Any “average” you have from modern data recording is at best a parody of a joke of a data set that can not even begin to come close to the ranges of what the planet does. When ever it wants to. With us or without us.
Anyone have a Chaiten update? It was still blowing and picking up steam last time I looked. The earthquake storm outlined a magma reservoir of super volcano size and if the venting continues for a year or two, we are setting up for a caldera collapse. When that happens, it’s going to be a very bad day world wide with dramatic cold and crop failures. All you can do is hope Chaiten and Yellowstone both decide that they can wait a few more hundreds or thousands of years before they let loose…
From:
http://volcanism.wordpress.com/2008/06/11/chaiten-update-11-june-2008/
The LP [long period] earthquakes have been sporadic and HB [hybrid] earthquakes and/or tremors have not been detected, which indicates a new repressurization of the internal system and/or a new injuection of magma into the upper system of the volcano.
Bearing the above in mind and considering that a new repressurization of the system, with an increase in explosivity and rate of emission of pyroclasts, cannot be ruled out, SERNAGEOMIN maintains Volcanic Red Alert.
JET (19:36:15) : If Milankovich cycles are solely responsible for glaciation, would not the Earth experience a continuous cycle of glacial advance and retreat?
How do we explain the geological record that suggests glaciation is confined to periods of several million years separated by about 200 million years?
The Solar System completes its orbit around the centre of the Milky Way Galaxy once each 226 million years – can periods of continental glaciation have an extra-Solar System cause? One that may be modified in some way by Milankovich’s Cycles – but not caused primarily by those relatively short (geologically speaking) variations in planetary orientation and orbit?
Well, this guy seems to have worked it out (and rather like you suggested):
http://www.sciencebits.com/ice-ages
I’m not sure what the fuss is about. This paper seems to be in accord with many that have gone before and in line with the consensus view. The CO2 lag has long been a feature of climate science (posited decades ago and firmed up from the mid-90s. It is mentioned in the last 2 IPCC docs.
I assume that this paper provides finer resolution on dating (wasn’t willing to pay to view), but the basic conclusions, as put in the press briefing, are the same as climate scientists have been working with for more than a decade.
While news of a ‘confirmed’ CO2 lag seems to have caught the ‘skeptics’ by surprise, it’s old news, and doesn’t remotely undermine the theory of what wil occur under current conditions (where the CO2 rise preceedes any significant glacial/deglacial event).
I’m sure the paper is interesting and will read it when and if a publicly available copy arrives on the internet. But the title of the top post is years out of date.
I hope this is not an attempt to revive the chicken and egg argument on this topic. We should know better by now (see – amplification).
[insert – Anthony, I below cite small fragments of the full paper “The Last Glacial Maximum”, which I purchased while writing this post. If you think that these quotes go beyond fair use, would you mind deleting just those parts and posting the rest?]
Having re-read the title of the top post (I glanced at it at first), I think it is misleading. It certainly misled me in my previous post.
Unless there is a specific accounting in the paper itself about how much of the total warming during deglaciation was contributed to by various components (insolation, albedo, GHG changes) – and which is unmentioned in the top post – then there is no information from the press briefing that justifies which was the ‘main driver’ of global temperature changes. All that is discussed in the press briefing is the timing of events, specifically of Northern Hemispheric glacial retreat. I’ll repeat the bolded part in the top post.
Having more than passing familiarity with the literature on this topic, I can confirm that the phasing of ice sheets/GHG increase – which drove which – has been the subject of vigorous debate. What is not covered by the above quote, is that the remarks concern the Northern Hemisphere ice (see below).
However, the title of the top post reads:
‘Main driver’ in the literature refers to the predominant forcing resulting in total temp changes – NOT to the first in the timing of events. In which case, “Insolation changes main driver” would be the lesson here – but that’s not the thrust of the paper. As it says in the press briefing quote, “Solar radiation was the trigger that started the ice melting, that’s now pretty certain” – and that has been ‘pretty certain’ for a decade. The paper is about ice sheet/GHG sequencing.
There is no reason why the sequence of events postulated in this paper should make a big difference to the generally understood contribution to warming of various forcings in late quaternary deglaciations. The relevance to current conditions lies with the amplification provided by GHGs in past deglaciations, not with the timing of events.
***********************************************************
[I paid for the article while writing this and have reviewed it]
I will cite small fragments of the paper pertinent to this discussion (thereby remaining within fair use parameters).
The paper is discussing here what triggered glacial melt in the Northern Hemisphere – whether insolation changes, CO2 or SSTs in the tropical Pacific. One conclusion is that Pacific SSTs cannot have contributed to the termination of the LGM.
There is no discussion of the strength of relative contributions, just the timing. There is, however, some pertinent commentary in the concluding paragraph.
(Emphasis mine)
ref – The Last Glacial Maximum
Peter U. Clark, Arthur S. Dyke, Jeremy D. Shakun, Anders E. Carlson, Jorie Clark, Barbara Wohlfarth, Jerry X. Mitrovica, Steven W. Hostetler, A. Marshall McCabe
Science 7 August 2009:
Vol. 325. no. 5941, pp. 710 – 714
DOI: 10.1126/science.1172873
That still leaves room for CO2 being a significant, or even main ‘driver’ of global warming during the last glacial termination. The chief proposal in the paper is that insolation changes triggered Northern Hemispheric glacial retreat at termination of the LGM, rather than CO2, and that sea level changes were initially a result of glacial melt. Globally, the phasing is less certain according to the paper. There are differences in sequencing regionally that do not accommodate firm conclusions.
Forgot to unbold the title of the paper referenced. Apologies.
It seems to me that heat is the frictional energy released by rubbing two scientists together resulting in ever increasing thermal talk.
Nasif Nahle (00:07:37) :
Heat is not a form of energy, but it is energy in transit. If that energy is not emitted and/or absorbed, but stored into a system, it’s not heat, but internal energy, i.e. potential and kinetic energy.
A definition has to be useful, and the definition of ‘heat’ you offer is not. On the contrary, the various sources you quote go to great length to explain why their definition of ‘heat’ is not what everybody thinks it is. It is useful to be able to talk about the ‘heat content’ [of the oceans, for example]. What would you say if not that? How about ‘the potential and kinetic energy of the oceans’ ? what a stilted and cumbersome [and hence useless – as it will not be used] expression. As I said the problem stems from an ambiguity in the English language. Other languages do not have that problem, e.g. German or Danish. I asked you about Spanish. You didn’t answer. Your definition does not buy you anything. Language will evolve to maximize communication, so ‘heat’ is what you put in by ‘heating’ something, or that which is lost when cooling something. Very sensible, useful, and without any confusion.
What do you think about Van Ness?
Who?
Adam Grey (03:45:29) :
The melting was first caused by more solar radiation,
There is a possible point of confusion between ‘radiation’ and ‘insolation’. Can you tell from the paper which is meant.
Geoff Sherrington (00:07:47) :
Leif, I note your comment “The VSOP82 theory is thought to be good to one million years, and the improved VSOP87 to much longer.” But this leaves me wondering about climate shifts on Earth that might not be explained by hindcasting these models.
Those shifts we can’t say much about, as there are just too many things that can vary, e.g. volcanic activity. People that believe in the cosmic ray hypothesis invoke galactic spiral arm passages and the like and find periodicities, but forget that the modulation of cosmic rays is also determined by random events, such as nearby supernova explosions and [random] long-term variations of the Earth’s magnetic field. BTW, the latter is the most important modulator of cosmic rays, much more important than the Sun and the solar wind. See e.g. http://www.leif.org/research/CosmicRays-GeoDipole.jpg where the large-scale variation is due to the Earth’s magnetic field changes and the little wiggles are solar related changes.
Leif Svalgaard (07:26:12) :
A definition has to be useful, and the definition of ‘heat’ you offer is not. On the contrary, the various sources you quote go to great length to explain why their definition of ‘heat’ is not what everybody thinks it is. It is useful to be able to talk about the ‘heat content’ [of the oceans, for example]. What would you say if not that? How about ‘the potential and kinetic energy of the oceans’ ? what a stilted and cumbersome [and hence useless – as it will not be used] expression. As I said the problem stems from an ambiguity in the English language. Other languages do not have that problem, e.g. German or Danish. I asked you about Spanish. You didn’t answer. Your definition does not buy you anything. Language will evolve to maximize communication, so ‘heat’ is what you put in by ‘heating’ something, or that which is lost when cooling something. Very sensible, useful, and without any confusion.
What do you think about Van Ness?
Who?
It’s not my definition, but the definition of all physicists and engineers around the world, except for you and your “star” physicist.
Instead saying “Heat content of the oceans”, I would say it correctly, i.e. Energy content of the oceans”. And yes, I can say “The potential and kinetic energy of the oceans”, because both are stored in the system “oceans”.
As I have said, it’s not a problem of ambiguity in the language, but a confusion spread out by I don’t know whom, but that was grasped by you. You said the kinetic energy was heat and it is impossible because heat is energy out of the system’s boundaries, being transferred towards other systems, while kinetic energy is internal energy.
Hendrick C. Van Ness is a distinguished professor of chemical engineering at Rensselaer Polytechnic Institute. He’s unsurpassed as an expert in the field. Well, H. C. Van Ness included in his book Understanding Thermodynamics, on PAGE 17, the definition of heat. Here is it:
“Remember that Q is a term which is included to account for energy changes in the surroundings. However, we call it heat because it is energy transferred across the boundary of the system as a result of a temperature difference.” (Bolds are mine).
I’ve shown many authors who confirm what I have said with respect to the difference between kinetic energy and heat. Now, show me a single author who says that the kinetic energy is the same as heat.
If short term oceanic oscillations can overcome CO2 as a temperature driver (which is admitted to by the “consensus”), who is to say that CO2 can overcome long term oceanic oscillations as the driver? On what basis?
Remember your basic geography.
1. Major sea level changes can DRASTICALLY change oceanic oscillations in short order, setting up major weather pattern variations that will persist until sea level changes again. Think of all the land bridges that have formed (either through ice or through exposed land) and then been overcome by sea water once again. And think how this would change oscillations. These processes would completely overwhelm what I think is a rather steady state, by comparison, affect of greenhouse gas warmth.
2. Changes in ice ages brought on by this orbital wobble will also drastically change freshwater access to salt water circulation patterns. This is no small issue at the pole and a broader area in latitude than just the Arctic Circle.
3. CO2 is such a small player due to plants sucking it out of the atmosphere as fast as you can pump it in. I don’t see how it can be a major driver, or even a minor driver compared to short term and long term weather pattern variation drivers.
*********
crosspatch (12:23:46) :
But having said that … there certainly is some “trigger” that very rapidly causes a state change from glaciation to interglacial and back. This change is apparently not gradual at all and happens very quickly … over the span of a human lifetime. Also, climate tends to be very unstable during glacial periods with extreme changes in climate happening very quickly. Areas can change from forest or grassland to tundra and back again in only a couple of human generations.
This “trigger” could be any number of things … a major volcanic eruption at just the right moment … a change in jet stream location … who knows? We will be finding out “soon”.
*******
crosspatch, the trigger IMHO is prb’ly a major ocean-current switch (I’m not sure what else it could be). What that would look like I don’t think anyone knows because the current “interglacial” pattern is all we’ve seen.
There’s some evidence that the high-latitude Arctic ocean is much more ice-free during glacial than interglacial periods (which provides the extra snow for the ice-sheets), even tho that goes against common sense.
What would cause such an ocean current change? Some computer models by Gildor-Tziperman (search google) suggest at the end of the interglacials the Arctic ocean becomes ice-free even during much of the winter, providing far more evaporation and snow than the high arctic gets nowadays, and changing ocean currents in a way that keeps the Arctic ocean slightly warmer than now! This “triggers” a new glacial period.
Who may define “HEAT”?
One of these days the “Bureau International des Poids et Mesures” (the brotherhood of physicists) will have perfected the SI and can start to define all physical quantities and their names.
Until then I propose to listen to the great ISAAC ASIMOV (who wrote books about physics, too):
“The heat content of a system is the total internal energy of the molecules making it up. The “internal energy” of a substance consists of the kinetic energy of its constituent particles plus the energy involved in the intermolecular attractions.”
Isaac Asimov, Understanding Physics
Leif Svalgaard (07:30:12) :
— “The melting was first caused by more solar radiation”
— There is a possible point of confusion between ‘radiation’ and ‘insolation’. Can you tell from the paper which is meant.
Hi Leif,
I think it’s clear from the concluding paragraph I quoted earlier:
From what I can make of the rest of the doc, ‘solar radiation’ isn’t a feature (the term is not used).
I think the quote from the press statment was casual use. Wherever I’ve read on this subject, insolation has been considered as the trigger for ice ages, with the debate around whether greenhouse warming initiated ice sheet melt or insolation changes at the poles. ‘Solar radiation’ was probably used in lieu of insolation for public consumption.
Pamela Gray (08:05:33) :
If short term oceanic oscillations can overcome CO2 as a temperature driver (which is admitted to by the “consensus”), who is to say that CO2 can overcome long term oceanic oscillations as the driver? On what basis?
Remember your basic geography.
3. CO2 is such a small player due to plants sucking it out of the atmosphere as fast as you can pump it in. I don’t see how it can be a major driver, or even a minor driver compared to short term and long term weather pattern variation drivers.
That’s because your basic premise is wrong, plants don’t “suck it out of the atmosphere as fast as you can pump it in”, far from it, that’s the whole point!
Hi Pamela,
If short term oceanic oscillations can overcome CO2 as a temperature driver (which is admitted to by the “consensus”), who is to say that CO2 can overcome long term oceanic oscillations as the driver? On what basis?
On the basis that oceanic oscillations are.. oscillations. For the current interglacial period, ocean/atmosphere currents have wobbled around a mean. The ‘greenhouse’ effect with increasing GHGs in the post-industrial era has a non-oscillating rhythm (positive in terms of tropospheric temps). Temperature changes from oceanic oscillations (weather/noise) is overwhelmed, in terms of temperature, by the ‘greenhouse’ signal. One of the larger oscillating effects, ENSO, ascillates to produce a maximum range of 0.4C (+/-0.2C). The centennial (ie, long-term) trend is larger than that.
1. Major sea level changes can DRASTICALLY change oceanic oscillations in short order, setting up major weather pattern variations that will persist until sea level changes again. Think of all the land bridges that have formed (either through ice or through exposed land) and then been overcome by sea water once again. And think how this would change oscillations. These processes would completely overwhelm what I think is a rather steady state, by comparison, affect of greenhouse gas warmth.
If you’re speaking of glacial change periods, there has been debate on this, but most papers, including this one, posit that GHG changes have a major affect on temps – and sea level via warming. At the same time, i believe the paper leading this thread is saying that initial sea level rise is caused by melting ice (in the NH).
I would hardly describe both deglacial and post-industrial GHG rises as ‘steady state’.
2. Changes in ice ages brought on by this orbital wobble will also drastically change freshwater access to salt water circulation patterns. This is no small issue at the pole and a broader area in latitude than just the Arctic Circle.
The paper mentions fresh water pulses (I don’t feel qualified to interpret). For deglaciation:
3. CO2 is such a small player due to plants sucking it out of the atmosphere as fast as you can pump it in. I don’t see how it can be a major driver, or even a minor driver compared to short term and long term weather pattern variation drivers.
I think you are confusing GHG equlibrium with the biannual fluctuations evident in the famous Keeling curve. Plants (and the oceans and other carbon sinks) have a limited capacity – otherwise we would still be at the ~280 ppm CO2 in the atmos pre-industrial. As we now have 36% more CO2 in the air since the industrial revolution (380+ ppm), clearly the plants aren’t taking it all up. That which is taken up in the Northern Hemispheric growing season, is greatly re-emitted from decaying foliage in the cold seasons. Bending an analogy to the aquatic seems fit – I’d say the CO2 rise is like the tide coming in: the waves come and go, but the water creeps up the shore inexorably. The sand-castle seems safe at first, but eventually it will succumb to the tide.
PDO, AMO, ENSO – these are oscillating ocean/atmosphere systems. There is some agreement with temp variations, particularly ENSO, but none of them account for the long-term warming signal. They are the waves, GHG warming is the tide. I think this is generally accepted by all now. The question that seems to matter is – how long before the tide reaches the sand-castle?
Alexej Buergin (09:10:08) :
Who may define “HEAT”?
One of these days the “Bureau International des Poids et Mesures” (the brotherhood of physicists) will have perfected the SI and can start to define all physical quantities and their names.
Until then I propose to listen to the great ISAAC ASIMOV (who wrote books about physics, too):
“The heat content of a system is the total internal energy of the molecules making it up. The “internal energy” of a substance consists of the kinetic energy of its constituent particles plus the energy involved in the intermolecular attractions.”
Isaac Asimov, Understanding Physics
I have no conflicts with Asimov’s description; however, we cannot say the internal energy of a system is heat, but the total energy possessed by a system that includes also to potential energy, because heat is energy leaving the system across the boundaries of that system.
On the other hand, specific internal energy is internal energy per mass of the substance in question. It is clear that heat is not into the system, but it has crossed the boundary of the system towards another system.
Asimov would have been right if he would have said that he was considering heat and energy were the same thing, which is not real. Heat is energy, but not every form of energy is heat.
Nonetheless, I agree with you on the convenience of not using ambiguous terms.
Felix will be all over this (if he is not already). Again, although I don’t believe it will be “the end of the world” I do wonder about “something” either happening or starting in the 2012 / 2013 time frame.
Nasif Nahle (07:59:23) :
Instead saying “Heat content of the oceans”, I would say it correctly, i.e. Energy content of the oceans”.
And this is incorrect. The oceans currents have bulk kinetic energy, so is part of the energy content of the oceans, but is not heat energy, because that is the random, disorganized kinetic energy, but the kinetic energy of the bulk flow. Nobody is saying that kinetic energy is heat, but rather that heat is the kinetic energy of the random, disorganized motions. This is your confusion. The heat is that part of the total energy that can be transferred without applying any forces, and is still there even if not transferred or ‘in transit’. You can also meaningfully say that ‘heat is added’ to the system [which then contains more heat] and it is in this sense the word is used in the second law of thermodynamics.
Nasif Nahle (10:09:35) :
heat is energy leaving the system across the boundaries of that system.
Perhaps this will help: The unit of heat is Joule, because it is an ‘amount’ which you can move from one place to another. If it were a ‘transit’ [leaving], the unit would be Watt [Joule per second], namely leaving at such and such a rate, but the unit is Joule, not Watt.
Nasif Nahle (14:34:53) :
The carbon dioxide more than being an amplifier of warming effects (which definitively it is not) it’s a distributor of heat
It would seem to me that this statement of yours conflicts with your definition of heat, as you can only distribute something that is stored or contained, and you say that then it is no longer heat.